11.A mass on the end of a spring undergoes simple harmonic motion with a frequency of 0.5 Hz. If the attached mass is reduced to one quarter of its value, then the new frequency in Hz is

12.A clock P is based on oscillation of a spring and another clock Q is based on pendulum motion. Both the clocks run at the same rate on Earth. Both the clocks are then taken to a planet having same density as Earth but twice the radius. Then

13.The length of a seconds pendulum is approximately

14.The time period of a mass suspended from a spring is 5 s. The spring is cut into four equal and the same mass is now suspended from one of its parts. The period is now

15.A solid copper sphere is suspended from a massless spring. The time period of oscillation of the system is 4 s. The sphere is now completely immersed in a liquid whose density is 1/8th that of brass. The sphere remains in liquid during oscillation. Now the time period is: